1. Field of the Invention
The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus comprising a pump mechanism for sucking waste ink.
2. Related Background Art
A recording apparatus such as a printer, a copying machine or a facsimile terminal equipment is constituted to record an image consisting of dot patterns onto a recording medium such as a paper or plastic sheet, based on image information.
The recording apparatus can be classified as an ink jet, wire dot-matrix, thermal or laser beam system. According to the ink jet system (ink jet recording apparatus) the ink is discharged from a recording head for depositing ink onto a recording medium.
This ink jet recording apparatus is a nonimpact type having such features as low noise, high-density and high-speed recording ability, and is given color image recording capability by the use of color inks.
In the ink jet recording apparatus as described above waste ink may sometimes collect on a discharge port face of a recording head due to a fine mist of ink floating with a recording medium, or the splashing of discharged ink from the recording medium.
If waste ink as mentioned above may adhere to the discharge port face of the recording head, the ink discharge direction or speed may change, or the particle sizes of discharged ink droplets may be dispersed, so that the quality of recording may be decreased.
As means for preventing such a phenomenon, an ink jet recording apparatus is provided with a suction station for sucking waste ink as above described.
However, in a conventional ink jet recording apparatus, a pump for the suction station is provided with a valve which opens or closes, in which waste ink is sucked by a piston reciprocating within a cylinder. The pump with such a constitution had a problem in that the repeating mechanism of the valve might malfunction due to ink collected on it. However, since few troubles originating from the problem occurred, a fundamental resolution was not achieved.
Thus, the present inventors examined a constitution in which contact members are used for the valve function, thereby eliminating the open/close valve mechanism, but a new problem occurred. That is, there is an advantage that this embodiment's construction is simple, (but the fouling due to collected ink becomes conspicuous within the apparatus.) This fouling was often seen particularly on a head surface within a cap. A detailed examination of this phenomenon by a present inventor showed that a back flow from the inside of the pump toward the cap is generated.